Technical Abstract:
Previous studies have demonstrated that condensed tannin-rich forages such as sericea lespedeza can control gastrointestinal nematode infection (GIN) in goats. The objective of three experiments (EXP) was to determine the influence of high tannin grain sorghum on GIN in goats. Naturally infected Boer crossbred animals were used with 16 mixed sex goats at 124 ± 2.9 days of age in EXP 1, 24 mixed sex goats at 160 ± 3.6 days of age in EXP 2 and 22 male goats at 259 ± 3.0 days of age in EXP 3. Animals were removed from pasture and placed on concrete-slatted (EXP1) or expanded metal flooring (EXP 2 and 3) at d –7 (EXP 1 and 3) or d –28 (EXP 2; d 0 = first day of sorghum feeding). Goats were fed diets containing high or low tannin grain sorghum (HI or LO diets, respectively with equal numbers of goats per treatment). Packed cell volume (PCV; sera/packed RBC*100%), FEC and FAMACHA® eyelid color scores (EYE; 1 to 5 with 1 = red and 5 = white; EXP 1 only) were recorded on d 0 and then every 7 d for 21 d (14 d for EXP 3). Animals were treated with an anthelmintic when PCV dropped below 20%. For EXP 1, percentage of animals dewormed (DE), FEC, PCV and EYE were not influenced by treatment and averaged 13.6 ± 4.5%, 620 ±139 eggs per gram (epg), 23.1 ± 0.7% and 3.2 ± 0.12, respectively for all animals. As expected, EYE and PCV were negatively related (r = -0.45; P < 0.001). For EXP 2, there was no influence of treatment on PCV (28.8 ± 0.5%) or FEC, however, there was an effect of day (P < 0.001) in which all animals had higher FEC on d0 (1956 ± 219 epg) than any other sampling day. In EXP 3, again, there was no effect of treatment on FEC (2992 ± 591 epg) or PCV (25.1 ± 0.5%). Although high tannin forages such as serecia lespedeza have been found to reduce FEC in small ruminants, in the present studies, high tannin grain sorghum (which may contain a different type of tannin than serecia) did not influence FEC or PCV in goats.